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Old 07-18-2012, 10:57 PM
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edd5 edd5 is offline
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Join Date: Feb 2012
Location: Florida panhandle
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Vehicle: 2012 Ram 1500 SLT
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Engine: 2009-20?? 345ci (5.7L) Hemi V8 390hp 407lb/ft
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If you are looking at the EVIC MPG you need to be aware that it is calibrated for your stock tire size. Going to a larger diameter tire you will actually be going a bit further with each revolution (your speedo will be off a bit too) but your EVIC doesn't know this. If your stock tires were the 33's when your speedo reads 70 your are really doing 74. In a nutshell, you are going further than your odometer says you are. You do lose a little mileage due to the tires being heavier (weight penalty) but it isn't that much. Try doing a manual calculation correcting for the size difference. Your ECM can only be programmed for up to a 33" tire so no help from the dealer on this. You could add an aftermarket box (like a Hypertech) to correct but it really isn't worth it.
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